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| United States Patent |
5,155,157
|
|
Statz
, et al.
|
October 13, 1992
|
Compositions useful in the manufacture of golfballs
Abstract
The invention provides compositions useful in the manufacture of one-, two-
and three-piece golfballs comprising blends of a copolyetherester or
copolyetheramide, an expoxy-containing compound, and an acid-containing
ethylene copolymer ionomer.
| Inventors:
|
Statz; Robert J. (Kennett Square, PA);
Braemer; Jon P. (Wilmington, DE);
Hagman; John F. (Wilmington, DE)
|
| Assignee:
|
E. I. du Pont de Nemours and Company (Wilmington, DE)
|
| Appl. No.:
|
681431 |
| Filed:
|
March 26, 1991 |
| Current U.S. Class: |
524/423; 524/432; 524/513; 524/514; 524/908 |
| Intern'l Class: |
C08K 003/30; C08K 003/18 |
| Field of Search: |
524/423,432,114,513,514,908
|
References Cited
U.S. Patent Documents
| 3671477 | Jun., 1972 | Nesbitt | 524/424.
|
| 4858924 | Aug., 1989 | Saito et al. | 273/218.
|
| 4919434 | Apr., 1990 | Saito | 273/235.
|
| 4955966 | Sep., 1990 | Yuki et al. | 524/908.
|
| Foreign Patent Documents |
| 2164342 | Mar., 1986 | GB.
| |
Primary Examiner: Michl; Paul R.
Assistant Examiner: Szekely; Peter
Attorney, Agent or Firm: Evans; Craig H.
Parent Case Text
This application is a continuation-in-part of application Ser. No.
07/634,793 filed Dec. 27, 1990, now abandoned.
Claims
What is claimed is:
1. A three-piece golfball comprised of a center, an elastomeric winding and
a cover wherein the center comprises a thermoplastic composition
comprising:
a) 65-90 weight percent of a thermoplastic polymer selected from
copolyetheramides and copolyetheresters;
b) 1-10 weight percent of an epoxy-containing compound having sufficient
epoxy functionality readily available for reaction with the ionomer of c)
but insufficient epoxy functionality to produce a thermoset composition;
and
c) the remainder, to total 100 weight percent of an acid-containing
ethylene copolymer ionomer.
2. The golfball of claim 1 wherein the thermoplastic composition further
contains about 40-60 weight percent, based on the total weight of the
composition of a filler having a density greater than or equal to about 4
gm/cc.
3. The golfball of claim 2 where the filler is selected from ZnO and
BaSO.sub.4.
4. The golfball of claim 1, 2 or 3 where a) is a copolyetherester.
5. The golfball of claim 1, 2 or 3 where b) is a glycidyl-containing
copolymer.
6. The golfball of claim 1, 2 or 3 where c) is an ethylene/(meth)acrylic
acid copolymer.
7. The golfball of claim 1, 2 or 3 where a) is a copolyetherester, b) is a
glycidyl-containing copolymer, and c) is an ethylene/(meth)acrylic acid
copolymer.
8. A three-piece golfball comprised of a center, an elastomeric winding and
a cover wherein the center comprises a composition selected from those of
claim 1, 2 or 3.
9. A three-piece golfball comprising a center, an elastomeric winding and a
cover wherein the center comprises about 35 weight percent (total) of a
polyetherester having a shore D hardness of 40, 1-5 weight percent of an
ethylene/n-butylacrylate (28%)/glycidyl methacrylate (5%) copolymer, about
10 weight percent of an ethylene/methacrylic acid (20%) copolymer highly
neutralized with Na cation, and about 50 weight percent ZnO.
10. A two-piece golfball comprised of a core and a cover wherein the core
comprises a thermoplastic composition comprising:
a) 50-65 weight percent of a thermoplastic polymer selected from
copolyetheramides and copolyetheresters;
b) 1-10 weight percent of an epoxy-containing compound having sufficient
epoxy functionality readily available for reaction with the ionomer of c)
but insufficient epoxy functionality to produce a thermoset composition;
and
c) the remainder, to total 100 weight percent, of an acid-containing
ethylene copolymer ionomer.
11. The golfball of claim 10 wherein the thermoplastic composition further
contains about 15-25 weight percent, based on the total weight of the
composition, of a filler having a density greater than or equal to about 4
gm/cc.
12. The golfball of claim 11 where the filler is selected from ZnO and
BaSO.sub.4.
13. The golfball of claim 10, 11 or 12 where a) is a copolyetherester.
14. The golfball of claim 10, 11 or 12 where b) is a glycidyl-containing
copolymer.
15. The golfball of claim 10, 11 or 12 where c) is an
ethylene/(meth)acrylic acid copolymer.
16. The golfball of claim 10, 11 or 12 where a) is a copolyetherester, b)
is a glycidyl-containing copolymer, and c) is an ethylene/(meth)acrylic
acid copolymer.
17. A two-piece golfball comprising a core and a cover, wherein the core
comprises 50-65 polymer weight percent of a thermoplastic polymer selected
from polyetheramides and polyetheresters, 1-10 polymer weight percent of
an epoxy-containing compound, 15-25 total weight percent ZnO and the
remainder to total 100 polymer percent, of an acid-containing ethylene
copolymer ionomer, the epoxy-containing compound having sufficient epoxy
functionality readily available for reaction with the ionomer but
insufficient epoxy functionality to produce a thermoset composition.
18. A two-piece golfball comprising a core and a cover wherein the core
comprises 50-65 polymer weight percent of a polyetherester having a shore
D hardness of about 40, 1-5 polymer weight percent of an ethylene/n-butyl
acrylate (28%)/glycidyl methacrylate (5%) copolymer; 40-45 polymer weight
percent of an ethylene/(meth)acrylic acid (20%) copolymer highly
neutralized with Na cations, and about 20 total weight percent ZnO.
19. A two-piece golfball comprised of a core and a cover, wherein the core
comprises a thermoplastic composition comprising:
a) between 30 and 50 polymer weight percent of a thermoplastic polymer
selected from copolyetheramides and copolyetheresters;
b) 1-10 polymer weight percent of an epoxy-containing compound having
sufficient epoxy functionality readily available for reaction with the
ionomer of d) but insufficient epoxy functionality to produce a thermoset
composition;
c) 15-25 total weight percent of a filler having a density greater than
about 5 gm/cc; and
d) the remainder, to total 100%, polymer percent of an acid-containing
ethylene copolymer ionomer.
20. The golfball of claim 19 where a) is a copolyetherester.
21. The golfball of claim 19 where b) is a glycidyl-containing copolymer.
22. The golfball of claim 19 where d) is an ethylene/(meth)acrylic acid
copolymer.
23. The golfball of claim 19 where a) is a copolyetherester, b) is a
glycidyl-containing copolymer, and d) is an ethylene/(meth)acrylic acid
copolymer.
24. The golfball of claim 19, 20, 21, 22, or 23 where the filler is
selected from ZnO, lead silicate and tungsten carbide.
25. A one-piece golfball comprising a thermoplastic composition comprising:
a) 40-65 polymer weight percent of a thermoplastic polymer selected from
copolyetheresters and copolyetheramides;
b) 1-10 polymer weight percent of an epoxy-containing compound having
sufficient epoxy functionality readily available for reaction with the
ionomer of d) but insufficient epoxy functionality to produce a thermoset
composition;
c) 5-20 total weight percent of a filler having a density greater than 4
gm/cc; and
d) the remainder, to total 100 polymer weight percent, of an
acid-containing ethylene copolymer ionomer.
26. The golfball of claim 25 where a) is a copolyetherester.
27. The golfball of claim 25 where b) is a glycidyl-containing copolymer.
28. The golfball of claim 25 where c) is an ethylene/(meth)acrylic acid
copolymer.
29. The golfball of claim 25 where a) is a copolyetherester, b) is a
glycidyl-containing copolymer, and d) is an ethylene/(meth)acrylic acid
copolymer.
30. The golfball of claim 25, 26, 27, 28, or 29 where the filler is
selected from ZnO and BaSO.sub.4.
31. A one-piece golfball comprising about 55 polymer weight percent of a
polyester having a shore D hardness of about 40, 1-5 polymer weight
percent of ethylene/n-butyl acrylate (28%/glycidyl methacrylate (5%)
copolymer, 40-45 polymer weight percent of an ethylene/methacrylic acid
(20%) copolymer highly neutralized with Na cations, and about 10 total
weight percent ZnO.
Description
FIELD OF THE INVENTION
The subject invention relates to the manufacture of one-, two-, and
three-piece golfballs, particularly with respect to polymer blend
compositions useful therein.
BACKGROUND OF THE INVENTION
There currently exist two general types of premium golfballs: a
"three-piece" ball which comprises a spherical molded center, having an
elastomeric thread-like material wound around it, covered with either a
thermoplastic or thermoset material; and a "two-piece" ball which
comprises a spherical molded core covered with a thermoplastic material.
The material used to mold the three-piece centers and the two-piece cores
has traditionally been a thermoset rubber, for example, polybutadiene
rubber. As with any thermoset material, however, there are major
disadvantages, such as the inability to recycle scrap materials and the
need for complex multistep manufacturing processes. Of course, three-piece
balls and two-piece balls are by their very nature more complicated and
costly to manufacture than the long sought after one-piece golfball, which
has yet to be successfully demonstrated except for limited flight
golfballs.
In an effort to overcome the deficiencies of the traditional thermoset
three-piece centers and two-piece cores, and in the quest to produce a
one-piece golfball, attempts have been made to utilize certain
thermoplastic materials in the molding of such centers, cores and
one-piece balls, but with limited success. For example, U.K. Patent
Application 2,164,342A describes moldable compositions comprising ionic
copolymers (or potentially ionizable acid copolymers) blended with certain
thermoplastic materials such as a polyester block copolyamide, a polyether
copolyamide, a copolyester and the like. Those compositions are said to be
useful as three-piece centers, two-piece cores and one-piece solid
golfballs, but they lack, e.g., durability. Therefore, there still exists
the need for a material that is thermoplastic, yet resilient and durable
enough, and imparting adequate compression, to be useful as a three-piece
center, two-piece core and a one-piece golfball.
SUMMARY OF THE INVENTION
The subject invention provides thermoplastic compositions that can be used
in the manufacture of one-, two- and three-piece golfballs. More
specifically, the subject invention comprises a composition for the
manufacture of a one-piece golfball comprising 40-65 polymer weight
percent of a thermoplastic polymer selected from copolyetheresters and
copolyetheramides; 1-10 polymer weight percent of an epoxy-containing
compound; 5-20 total weight percent of a filler having a density greater
than or equal to about 4 gm/cc, and the remainder, to total 100 polymer
weight percent, of an acid-containing ethylene copolymer ionomer.
In another embodiment, the subject invention provides a two-piece golfball
in which the core comprises 50-65 weight percent of a thermoplastic
polymer selected from copolyetheramides and copolyetheresters; 1-10 weight
percent of an epoxy-containing compound; and the remainder, to total 100
percent, of an acid-containing ethylene copolymer ionomer; preferably
provided that the thermoplastic polymer is present in greater than 50
volume percent of the composition.
In another embodiment, the subject invention provides a two-piece golfball
in which the core comprises between 30 and 50 polymer weight percent of a
thermoplastic polymer selected from copolyetheramides and
copolyetheresters; 1-10 polymer weight percent of an epoxy-containing
compound; 15-25 total weight percent of a filler having a density greater
than about 5 gm/cc; and the remainder, to total 100 polymer weight
percent, of an acid-containing ethylene copolymer ionomer.
In yet another embodiment, the subject invention provides a three-piece
golfball in which the center comprises 65-90 weight percent of a
thermoplastic polymer selected from copolyetheramides and
copolyetheresters; 1-10 weight percent of an epoxy-containing compound;
and the remainder, to total 100 weight percent of an acid-containing
ethylene copolymer ionomer.
DETAILED DESCRIPTION OF THE INVENTION
Because the species and relative ratios of the components used in the
practice of the subject invention vary somewhat depending upon the type of
golfball desired (i.e., one- piece, two-piece or three-piece), it is
useful to first consider the components themselves.
COMPONENT DESCRIPTION
The thermoplastic polymer component of the subject invention is selected
from copolyetheresters and copolyetheramides, both classes of polymers
being well known in the art. The copolyetheresters are discussed in detail
in, e.g., U.S. Pat. Nos. 3,651,014; 3,766,146; and 3,763,109. They are
comprised of a multiplicity of recurring long chain units and short chain
units joined head-to-tail through ester linkages, the long chain units
being represented by the formula
##STR1##
and the short chain units being represented by the formula
##STR2##
where G is a divalent radical remaining after the removal of terminal
hydroxyl groups from a poly(alkylene oxide) glycol having a molecular
weight of about 400-6000 and a carbon to oxygen ratio of about 2.0-4.3; R
is a divalent radical remaining after removal of hydroxyl groups from a
dicarboxylic acid having a molecular weight less than about 300; and D is
a divalent radical remaining after removal of hydroxyl groups from a diol
having a molecular weight less than about 250; provided said short chain
ester units amount to about 15-95 percent by weight of said
copolyetherester. The preferred copolyetherester polymers are those where
the polyether segment is obtained by polymerization of tetrahydrofuran and
the polyester segment is obtained by polymerization of tetramethylene
glycol and phthalic acid. Of course, the more polyether units incorporated
into the copolyetherester, the softer the polymer. For purposes of the
subject invention, the molar ether:ester ratio can vary from 90:10 to
10:90, preferably 80:20 to 60:40; and the shore D hardness is less than
70, preferably about 40. The copolyetheramides are also well known in the
art as described in, e.g., U.S. Pat. No. 4,331,786. They are comprised of
a linear and regular chain of rigid polyamide segments and flexible
polyether segments, as represented by the general formula
##STR3##
wherein PA is a linear saturated aliphatic polyamide sequence formed from
a lactam or aminoacid having a hydrocarbon chain containing 4 to 14 carbon
atoms or from an aliphatic C.sub.6 -C.sub.9 diamine, in the presence of a
chain-limiting aliphatic carboxylic diacid having 4-20 carbon atoms; said
polyamide having an average molecular weight between 300 and 15,000; and
PE is a polyoxyalkylene sequence formed from linear or branched aliphatic
polyoxyalkylene glycols, mixtures thereof or copolyethers derived
therefrom said polyoxyalkylene glycols having a molecular weight of less
than or equal to 6000 and n indicates a sufficient number of repeating
units so that said polyetheramide copolymer has an intrinsic viscosity of
from about 0.8 to about 2.05. The preparation of these polyetheramides
comprises the step of reacting a dicarboxylic polyamide, the COOH groups
of which are located at the chain ends, with a polyoxyalkylene glycol
hydroxylated at the chain ends, in the presence of a catalyst such as a
tetraalkylorthotitanate having the general formula Ti(OR).sub.4, wherein R
is a linear branched aliphatic hydrocarbon radical having 1 to 24 carbon
atoms. Again, the more polyether units incorporated into the
copolyetheramide, the softer the polymer. The ether:amide ratios are as
described above for the ether:ester ratios, as is the shore D hardness.
The epoxy-containing compound component of the subject invention can be any
compound that has an epoxy functionality readily available for reaction
with the carboxylic acid groups in the ethylene copolymer ionomers
detailed below. Such compounds include, for example, epoxidized oils such
as epoxidized soy bean oil, epoxidized elastomers such as epoxidized
natural rubber or epoxidized polybutadiene rubber, or an epoxy-containing
copolymer E/X/Y wherein E is ethylene, X is a softening comonomer, for
example, an acrylate, methacrylate, vinyl ether or vinyl ester comonomer
present in 0-50 (preferably 0-35, most preferably 0-30) weight percent of
the polymer, and Z is an epoxy-containing vinyl unsaturated monomer
present in 1-25 (preferably 1-20, most preferably 1-15) weight percent of
the polymer; such copolymers include without limitation, ethylene
copolymers copolymerized with one or more reactive monomers selected from
unsaturated epoxides of 4-11 carbon atoms, such as glycidyl acrylate,
glycidyl methacrylate, and vinyl glycidyl ether, and optionally
additionally containing alkyl acrylate, alkyl methacrylate, carbon
monoxide, sulfur dioxide and/or alkyl vinyl ether, where the alkyl radical
is from 1-12 carbon atoms. Preferred glycidyl containing copolymers for
use in the compositions of the present invention include ethylene/glycidyl
acrylate, ethylene/n-butyl acrylate/glycidyl acrylate, ethylene/methyl
acrylate/glycidyl acrylate, ethylene/glycidyl methacrylate,
ethylene/n-butyl acrylate/glycidyl methacrylate and ethylene/methyl
acrylate/glycidyl methacrylate copolymers. The most preferred
glycidyl-containing copolymers are ethylene/n-butyl acrylate/ glycidyl
methacrylate and ethylene/glycidyl methacrylate copolymers.
These glycidyl-containing ethylene copolymers are made by processes well
known in the art, e.g., by direct copolymerization of ethylene, glycidyl
methacrylate or glycidyl acrylate, and the above-defined acrylate or
methacrylate in the presence of a free-radical polymerization initiator at
elevated temperatures, preferably 100.degree.-270.degree. C. and most
preferably 130.degree.-230.degree. C., and at elevated pressures,
preferably at least 70 MPa, and most preferably 140-350 MPa.
The acid-containing ethylene copolymer ionomer component of the subject
invention includes E/X/Y copolymers where E is ethylene, X is a softening
comonomer such as acrylate or methacrylate present in 0-50 (preferably
0-25, most preferably 0-2) weight percent of the polymer, and Y is acrylic
or methacrylic acid present in 5-35 (preferably 10-35, most preferably
15-35) weight percent of the polymer, wherein the acid moiety is
neutralized 1-90% (preferably at least 40%, most preferably at least about
60%) to form an ionomer by a cation such as lithium*, sodium*, potassium,
magnesium*, calcium, barium, lead, tin, zinc* or aluminum (*=preferred),
or a combination of such cations. Specific acid-containing ethylene
copolymers include ethylene/acrylic acid, ethylene/methacrylic acid,
ethylene/acrylic acid/n-butyl acrylate, ethylene/methacrylic acid/n-butyl
acrylate, ethylene/methacrylic acid/iso-butyl acrylate, ethylene/acrylic
acid/iso-butyl acrylate, ethylene/methacrylic acid/n-butyl methacrylate,
ethylene/acrylic acid/methyl methacrylate, ethylene/acrylic acid/methyl
acrylate, ethylene/methacrylic acid/methyl acrylate, ethylene/methacrylic
acid/methyl methacrylate, and ethylene/acrylic acid/n-butyl methacrylate.
Preferred acid-containing ethylene copolymers include ethylene/methacrylic
acid, ethylene/acrylic acid, ethylene/methacrylic acid/n-butyl acrylate,
ethylene/acrylic acid/n-butyl acrylate, ethylene/methacrylic acid/methyl
acrylate and ethylene/acrylic acid/methyl acrylate copolymers. The most
preferred acid-containing ethylene copolymers are ethylene/methacrylic
acid, ethylene/acrylic acid, ethylene/(meth)acrylic acid/n-butyl acrylate,
ethylene/(meth)acrylic acid/ethyl acrylate, and ethylene/(meth)acrylic
acid/methyl acrylate copolymers. The manner in which the ionomers are made
is well known in the art as described in, e.g., U.S. Pat. No. 3,262,272
(Rees).
The optional filler component of the subject invention is chosen to impart
additional density to blends of the previously described components, the
selection being dependent upon the type of golfball desired (i.e.,
one-piece, two-piece or three-piece), as will be more fully detailed
below. Generally, the filler will be inorganic having a density greater
than about 4 gm/cc, preferably greater than 5 gm/cc, and will be present
in amounts between 5 and 65 weight percent based on the total weight of
the polymer components. Examples of useful fillers include zinc oxide,
barium sulfate, lead silicate and tungsten carbide, as well as the other
well known corresponding salts and oxides thereof. It is preferred that
the filler materials be non-reactive with the polymer components described
above. Additional optional additives useful in the practice of the subject
invention include acid copolymer waxes (e.g., Allied wax AC143 believed to
be an ethylene/16-18% acrylic acid copolymer with a number average
molecular weight of 2,040) which assist in preventing reaction between the
filler materials (e.g., ZnO) and the acid moiety in the ethylene
copolymer; TiO.sub.2 which is used as a whitening agent; optical
brighteners; surfactants; processing aids; etc.
The specific combinations of components used in the practice of the subject
invention will in large part be dependent upon the type of golfball
desired (i.e. one-piece, two-piece or three-piece), as detailed below.
In general, the molding techniques used in the manufacture of one-piece,
two-piece, and three-piece balls are well known. It is preferable to use
runnerless molding techniques, most preferably valve gated, where the
polymer is injection molded into the cavity. This technology greatly
improves efficiency and cost as runners are eliminated, as is all of the
effort and cost relative to rework. In the case of one-piece balls, the
valve gate(s) can be disguised as a dimple in the ball eliminating the
need for secondary finishing of the gate vistige. Also most preferably,
the use of the traditional stack molding techniques can significantly
reduce costs and improve efficiency.
THREE-PIECE GOLFBALL PREFERRED EMBODIMENTS
As used herein, the term "three-piece ball" refers to a golfball comprising
a center made from the compositions of the invention, a traditional
elastomeric winding wound around the center, and a cover made from any
traditional golfball cover material such as Surlyn.RTM. ionomer resin,
balata rubber and the like. These three-piece golfballs are manufactured
by well known techniques as described in, e.g., U.S. Pat. No. 4,846,910.
For purposes of the subject invention, the center is made by injection
molding of the compositions of this invention. Those centers are then
placed into a winding machine in which the end of an elastomeric thread is
affixed to the molded center and the thread wound around the center to a
predetermined thickness. A dimple-patterned cover is then molded around
this wound center. For use as the center material for three-piece balls,
the preferred composition of the subject invention comprises 65-90 weight
percent of the thermoplastic component, 1-10 weight percent of the
epoxy-containing compound and the remainder, to total 100 weight %, of the
acid-containing ethylene copolymer ionomer. The most preferred
compositions of the invention for use as a three-piece center also contain
about 40-60 weight percent of the previously described filler material,
based on total weight of the three polymer components plus filler. The
most preferred thermoplastic component for use in the three-piece ball is
a copolyetherester; the most preferred epoxy-containing compound is a
glycidyl-containing ethylene copolymer; and the most preferred
acid-containing ethylene copolymer ionomer is an ethylene/methacrylic acid
or ethylene/acrylic acid copolymer. The three-piece ball that performs
most satisfactorily, as seen in the Examples below, contains a center
molded from a composition that comprises from about 35 weight percent
(total composition) of the polyetherester, described in Table 1 below as
"H1", 1-5 weight percent of an ethylene/n-butylacrylate (28%)/glycidyl
methacrylate (8%) copolymer, about 10 weight percent of an
ethylene/methacrylic acid (20%) copolymer highly neutralized with Na
cations to form the ionomer, about 50 weight percent ZnO, and about 5
weight percent Allied wax AC143. Note that these weight percentages are
given as a percent based on total composition to more clearly show the
relative proportion of components in an actual three-piece center
formulation.
TWO-PIECE GOLFBALL PREFERRED EMBODIMENTS
As used herein, the term "two-piece ball" refers to a golfball comprising a
core made from the compositions of the invention, and a cover made from
any traditional golfball cover material as discussed above. These
two-piece balls are manufactured by first molding the core from the
compositions of the subject invention, positioning these preformed cores
in an injection molding cavity using retractable pins, then injection
molding the cover material around the core. The most efficient way to
produce two-piece golf balls is to use runnerless molding techniques,
preferably valve gated, where the polymer is injection molded into the
cavity at the pole or poles instead of the equator as is commonly done.
The valve gate is disguised as a dimple in the ball. This technology
greatly improves the efficiency and cost of producing two-piece golf balls
as the runners are eliminated, as is all of the effort and cost relative
to rework. For use as the core material for two-piece balls, one preferred
composition of the subject invention comprises 50 to 65 polymer weight
percent of the thermoplastic component, 1-10 polymer weight percent of the
epoxy-containing compound, and the remainder to total 100 weight percent,
of the acid-containing ethylene copolymer ionomer; preferably provided
that the thermoplastic component is present in greater than 50 volume
percent of the composition. It is also preferred that such compositions
contain 15-25 total weight percent of the previously described filler
material. In another preferred composition, the thermoplastic component is
present between 30 and 50 polymer weight percent, the epoxy-containing
component present between 1 and 10 polymer weight percent, and the ionomer
the remainder to total 100 weight percent, but in such a composition the
filler material is necessarily present in 15-25 weight percent based on
total composition, and must have a density of greater than about 5 gm/cc
(e.g., zinc oxide, lead silicate or tungsten carbide). In both
embodiments, the most preferred thermoplastic component is a
copolyetherester; the most preferred epoxy-containing compound is a
glycidyl-containing ethylene copolymer; and the most preferred
acid-containing ethylene copolymer ionomer is an ethylene/(meth)acrylic
acid copolymer. The two-piece ball that performs most satisfactorily, as
seen in the Examples below, contains a core molded from a composition that
comprises 50-60 polymer weight percent of the polyetherester described in
Table 1, 1-5 polymer weight weight percent of an ethylene/n-butyl acrylate
(28%)/glycidyl methacrylate (5%) copolymer, 40-45 polymer weight percent
of an ethylene/(meth)acrylic acid (20%) copolymer highly neutralized with
Na cations to form the ionomer, about 20 total weight percent ZnO, and
about 5 weight percent Allied wax.
ONE-PIECE GOLFBALL PREFERRED EMBODIMENTS
As used herein, the term "one-piece ball" refers to a golfball molded in
toto from the compositions of the subject invention, i.e., not having
elastomeric windings nor a cover. The one-piece molded ball will have a
traditional dimple pattern and may be coated with a urethane lacquer or be
painted for appearance purposes. These one-piece balls are manufactured by
direct injection molding techniques under conditions described below in
Table 2B. For use in one-piece balls, the preferred composition of the
subject invention comprises 40 to 65 polymer weight percent of the
thermoplastic component, 1-10 polymer weight percent of the
epoxy-containing compound, 5-20 weight percent, based on the total weight
percent, of the previously described filler material and the remainder, to
total 100 polymer weight percent, of the acid-containing ethylene
copolymer ionomer. Again, the most preferred thermoplastic component is a
copolyetherester; the most preferred epoxy-containing compound is a
glycidyl-containing ethylene copolymer; and the most preferred
acid-containing ethylene copolymer ionomer is an ethylene/methacrylic acid
copolymer. The one-piece ball that performs the most satisfactorily, as
seen in the Examples below, is molded from a composition of the subject
invention comprising about 55 polymer weight percent of the polyetherester
described in Table 1, 1-5 polymer weight percent of ethylene/n-butyl
acrylate (28%)/glycidyl methacrylate (8%) copolymer, 40-45 polymer weight
percent of an ethylene/methacrylic acid (20%) copolymer highly neutralized
with Na cations to form the ionomer, about 10 total weight percent ZnO,
about 5 total weight percent AC143 Allied wax, and about 5 total weight
percent TiO.sub.2.
Those skilled in the art will appreciate that certain variations of the
compositions of the subject invention will also be useful in the
manufacture of one-piece and two-piece restricted flight golfballs, also
commonly known as range balls; the distance that such range balls can
travel being dependent upon the resiliency of the materials used and the
compression imparted. Further, the compositions of the subject invention
having flex modulus of about 14,000-30,000 (ASTM D790, procedure B),
preferably without filler, may also be employed as golfball cover
materials.
TESTING CRITERIA
In the Examples set out below, a number of testing criteria are utilized in
the evaluation of golfball performance: percent rebound, total distance
travelled, initial velocity, coefficient of restitution (COR) and
compression. Percent rebound is determined by dropping the ball (or
three-piece center/two-piece core) from a height of 100 inches and
measuring the rebound from a hard, rigid surface such as a thick steel
plate or a stone block; an acceptable result is about 65-80%. Total
distance is determined by striking a ball with a 10.5 degree loft driver
at a clubhead speed of 95 mph; an acceptable result is about 220-250 yds.
Initial velocity is the measured speed of the ball off a clubhead as
described for total distance (acceptable result approaching but less than
215 ft/sec as used in Table 2A) or the measured speed of the ball when hit
at 230 feet per second by an implement having a face angle of 13.degree.
with respect to the vertical (acceptable result approaching but less than
255 ft/sec as used in Table 1C). COR is measured by firing a golfball (or
two piece core) from an air cannon at a velocity determined by the air
pressure. The initial velocity generally employed is between 125 to 255
feet/second. The ball strikes a steel plate positioned three feet away
from the point where initial velocity is determined, and rebounds through
a speed-monitoring device. The return velocity divided by the initial
velocity is the COR; acceptable results are 0.550-0.750 at 180 ft/sec or
0.500-0.650 at 230 ft/sec. Compression is defined as the resistance to
deformation of a golfball, measured using an ATTI machine; an acceptable
result is about 70-120.
EXAMPLES 1, 2, 3; COMPARATIVE EXAMPLES C1, AND C2; AND CONTROL EXAMPLE.
These examples and comparative examples illustrate the preparation and
properties of centers for three-piece golf balls and of finished balls
from such centers. Blends for the thermoplastic centers of such balls were
prepared by extrusion in a twin screw extruder. The compositions are given
in Table 1, and extrusion conditions shown in Table 1A. These blends were
then molded into spheres of 1.08 in. diameter using an 8 oz. Van Dorn
Injection molding machine, with molding conditions shown in Table 1B.
Density and percent rebound were measured on these centers. The centers
were also made into three piece balls using conditions similar to those
described in U.S. Pat. No. 4,846,910 to Acushnet Corp., by winding with
natural rubber threads, and compression molding a cover on top of the
windings using a Surlyn.RTM. ionomer blend. As a control, the properties
of an Acushnet `Titleist DT` ball are shown. This ball is made of a
crosslinked (non thermoplastic) polybutadiene center, natural rubber
windings and the same ionomer cover used for the thermoplastic center
balls. All property measurements are shown in Table 1C.
TABLE I
______________________________________
CENTER COMPOSITIONS
Ex Add-
# Ref# Hytrel(H1)
EBAGMA(G1)
Ionomer
Filler
itive
______________________________________
1 62-4 35(78) 3(4) I1, 8(18)
F1, 51
A1
2 62-1 36(75) 2(4) I1, 10(21)
F1, 48
A1
3 41-5 41(73) 1(2) I2, 14(25)
F1, 40
A1
4 10-3 44(73) 1(2) I2, 15(25)
F2, 40
--
5 10-2 51(73) 1(2) I2, 18(25)
F2, 30
--
______________________________________
(Values are weight percentages. Percentages given in parentheses are on a
polymer only basis.)
H1 is a `Hytrel`, resin with composition:
18.2/0.3/72.3/9.1:terphthaloyl/TMTM/PTMEG2000/1,4 butane diol, plus an
antioxidant. PTMEG is polytetramethylene glycol. TMTM is
trimethyltrimellitoyl.
(G1)Ethylene/28% butyl acrylate/8.4% glycidyl methacrylate with a melt
index of 10.6.
(I1)Ethylene/20% methacrylic acid, 57% Na neutral., MI = 1
(I2)Ethylene/15% methacrylic acid, 52% Li neutral., MI = 1.8
(F1)Fisher Zinc Oxide
(F2)Wittaker Clark Barium Sulfate, Blanc Fix N
(A1)AC143 Ethylene/15.66% acrylic acid with Mn = 2040, Mw = 5670
TABLE 1A
______________________________________
EXTRUSION CONDITIONS FOR BALL COMPOSITIONS
Screw Die Rate
Speed Zone 1 Zone 2 Zone 3 Temp.degree.
lbs/ Vacuum
RPM Temp.degree. C.
Temp.degree. C.
Temp.degree. C.
C. hr In
______________________________________
150 161 194 202 207 16.4 26
______________________________________
TABLE 1B
______________________________________
MOLDING CONDITIONS FOR THREE PIECE CENTERS*
______________________________________
Temperatures Degrees C
Rear 174
Center 177
Front 177
Nozzle 171
Mold
Fixed 10
Movable 10
Pressures Kg/sq. cm.
Injection 1st stage 140
Injection Second Stage 84
Injection Hold 14
Cycle Times Sec:
Injection 10
Hold 300
Booster 7
Screw Retraction 1.75
Pad (cm) .05
Screw Speed (RPM) 55
Back Pressure (kg/sq. cm)
8.4
Mold Size 1.092 Inches Diameter (0.429 cm)
Part Size 1.08 Inches Diameter (0.425 cm)
______________________________________
*Prototype mold, limited cooling, two cavity
TABLE 1C
______________________________________
PROPERTIES OF THREE PIECE CENTERS OR BALLS
Ball
Center Veloc-
MI Density % Re- Compr. Wt. ity % Rej.
Ex# (1) (g/cc) bound ATTI (g) ft/sec.
(2)
______________________________________
1 11.1 1.71 67 85.9 45.2 250.9 0
2 17.6 1.56 69.6 85.9 43.8 251.8 7.1
3 20.0 1.45 67.4 97.2 42.2 252.0 17
C1 17.0 1.48 69.4 94.7 42.6 251.4 68
C2 22.0 1.31 70.5 98.0 41.0 253.0 62
Con- 70.0 77.3 45.2 252.8 22.7
trol
______________________________________
(1)Measured using ASTM D1238, with 10 Kg. wt at 220 deg. C.
(2)Percent Reject based on out of roundness as measured by a fluoroscope
on finished ball. Out of roundness is caused by the combined effect of
pressure due to winding and the heat associated with the compression
molding of the cover. Out of round balls behave unsatisfactorily, and
would have properties outside USGA standards.
The first three examples show that balls may be made satisfactorily with
respect to number of rejects, and these are actually less than in the case
of the thermoset center ball control. Compression is somewhat higher than
for the control, but within the acceptable range of about 70 to 120.
Initial velocity is below the acceptable maximum of 255. The % rebound is
comparable to the control center, and an indication of generally
acceptable performance. It will be noted however, that the best balls are
produced when the EBAGMA level is highest. In the two comparative
examples, while measured properties were acceptable, the level of rejects
was totally unacceptable. Comparative example C1 has a low level of
polyetherester and filler. Comparative example C2 has a very low level of
filler.
EXAMPLES 4, 5, AND 6; COMPARATIVE EXAMPLE C3 AND CONTROL EXAMPLE
These examples describe the preparation of blends for the core for two
piece golf balls, golf balls made therefrom, and the properties of the
cores and finished balls. The composition of these blends is shown in
Table 2. The blends were made using extrusion conditions the same as those
for three piece center compositions shown in Table IA. The blends were
molded into cores using conditions shown in Table 2B. The core is 1.5
inches in diameter. Balls were prepared by positioning preformed
thermoplastic cores in an injection molding cavity. The cores were
centrally positioned in the cavity by the use of retractable pins. A cover
of mixed `Surlyn` ionomer resin was then injection molded around the core.
Properties of the resultant cores or balls are shown in Table 2A.
TABLE 2
______________________________________
CORE COMPOSITIONS
Ex Add-
# Ref# Hytrel(H1)
EBAGMA Ionomer
Filler
itive
______________________________________
4 72-1 41(53) G2, 3(4) I1, 33(43)
F3, 19
A1,
4
5 8143- 42(52) G2, 3(4) I2, 35(44)
F4, 20
--
3
6 115-3 42(55) G1, 1(2) I1, 33(43)
F3, 19
A1,
4
C3 104-2 21(27) G3, 7(9) I3, 49(64)
F2, 22
--
C4 016R 43(56) 0 I1, 34(44)
F3, 19
A1,
4
______________________________________
Values are weight percentages. Percentages given in parenthesis are on a
polymer only basis.
H1, G1, I1, I2, A1, F2 as in Table 1.
G2 Ethylene/28% nbutyl acrylate/5.3% glycidyl methacrylate with a melt
index of 12.0
G3 Ethylene/34.5% nbutyl acrylate/5.3% glycidyl methacrylate with a melt
index of 6.0.
I3 Ethylene/15% methacrylic acid, 57% Na neutralized, MI = 1.2
F3 Zinc Oide, grade XX503R, Zinc Corp. of America.
F4 Barium Sulfate, `Barmite` 4.3 microns, Cyprus Corp.
TABLE 2A
__________________________________________________________________________
PROPERTIES OF TWO PIECE CORES OR BALLS
Core Ball
Durabil. Carry
Compr.
Hits/Break
Compr.
Reb. & Roll
Ex# ATTI at psi COR
ATTI % Velocity
COR
(yds)
__________________________________________________________________________
4 17/50, 20/40
.638
121 77 209.8
.614
236
5 118 74 208.0
.582
229
6 111 74 208.4
.586
235
C3 122 133 67.8
-- -- --
C4 4/50, 7/40
.635
CONTROL 111 81 213.5
.641
249
__________________________________________________________________________
The Control ball is a Ram LP ball which has a thermoset butadiene core and
a mixed ionomer cover. Coefficient of restitution for cores was measured
at 180 ft/sec. Coefficient of restitution for balls was measured using an
air canon with a pressure of 45 psi. which gives a velocity of about 230
ft./sec. Values for balls can be compared from one to another, but not
with the COR values for cores or the one piece balls shown below, which
are measured using different conditions. The test is used for general
guidance to ball performance.
Examples 4 and 5 indicate that zinc oxide and a high acid ionomer give
slightly superior resilience than barium sulfate and ionomer containing
lower acid levels. Properties of all the thermoplastic cores are
acceptable, though not quite equal to that of the control thermoset core
ball. Comparative Example C3 has a low Hytrel and a high ionomer level; as
a result, the compression is very high. High compression values indicate a
high force to compress, and a ball with a `hard` feel. Example C4 used a
blend with no epoxy-containing polymer. The blend was compared with
example 4 for coefficient of restitution and durability. Durability was
determined by firing from an air canon at the indicated pressure against a
steel rebound plate, and counting the number of hits before the ball
breaks. While it had a comparable coefficient of restitution, its
durability was extremely poor, indicating a strong need to compatibilize
the blend with the epoxy containing polymer.
TABLE 2B
______________________________________
MOLDING CONDITIONS FOR TWO PIECE CORES
AND ONE PIECE BALLS*
______________________________________
Temperatures Degrees C
Rear 183
Center 173
Front 173
Nozzle 177
Mold Front/Back 10
Melt 195
Pressures Kg/Square Cm
Injection 1st Stage 130
Injection 2nd Stage 110
Injection Hold 13
Cycle Times (sec)
Pac 10
Hold 480
Booster 10
Cure Time 15
Screw Retraction 5.35
Pad (cm) 0.6
Screw Speed RPM 55
Back Pressure (Kg/square cm)
Mold Diameter (cm) 3.88
______________________________________
*Prototype mold, limited cooling, four cavity
EXAMPLES 7, 8, 9 AND 10 AND CONTROL EXAMPLE
These examples illustrate the use of the thermoplastic blends of the
invention for use in one piece balls. The blends were made using extrusion
conditions as in Table 1A. Balls were molded using conditions as in Table
2B, except that the ball diameter was 1.65 inches. Compositions are given
in Table 3, and properties are shown in Table 3B.
TABLE 3
______________________________________
ONE PIECE BALL COMPOSITIONS
Ex Add-
# Ref# Hytrel EBAGMA Ionomer
Filler
itive
______________________________________
7 136-1 H1, 42(51)
G1, 3(4)
I3, 37(45)
F2, 17
T, 1
8 150-1 H2, 44(52)
G1, 3(4)
I3, 37(44)
F2, 15
T, 1
9 8143-3 H1, 42(52)
G1, 3(4)
I2, 35(44)
F4, 20
--
10 H003A H1, 46(56)
G2, 3(4)
I1, 34(41)
F3, 9.5
T, 4
A1, 4
______________________________________
Values are weight percentages. Percentages in parenthesis are on a polyme
only basis.
H1, G1, G2, I1, I2, I3, F2, F3, F4, A1 as in previous tables.
H2 is a `Hytrel` resin with composition:
27.4/7.9/44.8/19.5%:ter/isophthaloyl/PTMEG2000/1,4butane diol, plus an
antioxidant.
T is TiO2, grade R960 mfg. by the DuPont Company.
TABLE 3B
______________________________________
PROPERTIES OF ONE PIECE BALLS
Ex Melt Flow % Re- Durability
# (g/cc) Dens. bound Compr. COR (Hits)
______________________________________
7 3.0 1.16 64 83 .586 >200
8 5.3 1.17 -- -- .558 --
9 13.6 1.20 67 104 .602 >200
10 -- 1.12 -- 88 .653 --
Con- 1.14 -- 100 .737 100
trol
______________________________________
The control was a Wilson ULTRA two piece ball, with a thermoset butadiene
core and a `Surlyn` blend cover.
Coefficient of Restitution was measured using an air cannon with initial
ball velocity of 180 ft./sec. The results suggest that "soft"
polyetherester appears to give superior results to a harder grade (example
8), and a harder ionomer (more methacrylic acid as in example 10) is also
preferred.
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